A mouse model for X-linked Alport syndrome induced by Del-ATGG in the Col4a5 gene.

Alport syndrome (AS) is an inherited glomerular basement membrane (GBM) disease leading to end-stage renal disease (ESRD). X-linked AS (XLAS) is caused by pathogenic variants in the COL4A5 gene. Many pathogenic variants causing AS have been detected, but the genetic modifications and pathological alterations leading to ESRD have not been fully characterized. In this study, a novel frameshift variant c.980_983del ATGG in the exon 17 of the COL4A5 gene detected in a patient with XLAS was introduced into a mouse model in by CRISPR/Cas9 system. Through biochemical urinalysis, histopathology, immunofluorescence, and transmission electron microscopy (TEM) detection, the clinical manifestations and pathological alterations of Del-ATGG mice were characterized. From 16 weeks of age, obvious proteinuria was observed and TEM showed typical alterations of XLAS. The pathological changes included glomerular atrophy, increased monocytes in renal interstitial, and the absence of type IV collagen α5. The expression of Col4a5 was significantly decreased in Del-ATGG mouse model. Transcriptomic analysis showed that differentially expressed genes (DEGs) accounted for 17.45% (4,188/24003) of all genes. GO terms indicated that the functions of identified DEGs were associated with cell adhesion, migration, and proliferation, while KEGG terms found enhanced the degradation of ECM, amino acid metabolism, helper T-cell differentiation, various receptor interactions, and several important pathways such as chemokine signaling pathway, NF-kappa B signaling pathway, JAK-STAT signaling pathway. In conclusion, a mouse model with a frameshift variant in the Col4a5 gene has been generated to demonstrate the biochemical, histological, and pathogenic alterations related to AS. Further gene expression profiling and transcriptomic analysis revealed DEGs and enriched pathways potentially related to the disease progression of AS. This Del-ATGG mouse model could be used to further define the genetic modifiers and potential therapeutic targets for XLAS treatment.

Valproic acid enhances Oct4 promoter activity through PI3K/Akt/mTOR pathway activated nuclear receptors.

Valproic acid (VPA) has been shown to increase the reprogramming efficiency of induced pluripotent stem cells (iPSC) from somatic cells, but the mechanism by which VPA enhances iPSC induction has not been defined. Here we demonstrated that VPA directly activated Oct4 promoter activity through activation of the PI3K/Akt/mTOR signaling pathway that targeted the proximal hormone response element (HRE, -41∼-22) in this promoter. The activating effect of VPA is highly specific as similar compounds or constitutional isomers failed to instigate Oct4 promoter activity. We further demonstrated that the upstream 2 half-sites in this HRE were essential to the activating effect of VPA and they were targeted by a subset of nuclear receptors, such as COUP-TFII and TR2. These findings show the first time that NRs are implicated in the VPA stimulated expression of stem cell-specific factors and should invite more investigation on the cooperation between VPA and NRs on iPSC induction.